bin/install_megadrivers.py: Remove shebang and executable bit

Since the script is never executed directly, but launched by Meson as an
argument to the Python interpreter, those are not needed any more.

In addition, they are the reason this script was missed when I moved the
Meson buildsystem to Python 3, so removing them helps avoiding future
confusion.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

bin/install_megadrivers.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # encoding=utf-8
 # Copyright © 2017-2018 Intel Corporation